Comparative transcriptomics of the pheromone glands provides new insights into the differentiation of sex pheromone between two host populations of Chilo suppressalis

Abstract

Reproductive isolation between different host populations is often based on intraspecific sex pheromone differences. The mechanisms underlying these differences have not been thoroughly elucidated to date. Previous studies suggested that Chilo suppressalis has differentiated into rice and water-oat host populations, and these two populations manifest clear differences in sex pheromone titer and mating rhythm. Hence, this moth is an ideal model to investigate the endogenous mechanisms of intraspecific reproductive isolation. Here, we identified a series of putative genes associated with sex pheromone biosynthesis based on the C. suppressalis pheromone gland transcriptome data. Transcripts of most genes were at higher level in the rice population. Then we obtained 11 pivotal differentially expressed genes (DEGs). The expression levels of these DEGs exhibited a distinct increase in the rice population. Moreover, we also observed the expression rhythm of these DEGs is discrepant between two host populations. Our study offers a new understanding to elucidate the mechanisms of intraspecific reproductive isolation.

Figure 1

Analysis of DEGs in the pheromone gland transcriptome between rice (R) and water-oat populations (W) of C. suppressalis. (A) Distribution of upregulated and downregulated DEGs in each comparison; (B) Venn diagram of DEGs in different comparisons among the groups. Upregulations indicate that the genes have a higher expression in the rice population compared to the water-oat population.

Figure 2

Heatmap analysis of expression patterns of putative genes associated with sex pheromone biosynthesis at 0 h, 3 h and 6 h after the onset of scotophase between rice (R) and water-oat populations (W) in C. suppressalis. Prior to analysis, FPKM values of the genes were Z-score standardized. The heatmap was plotted using GraphPad Prism 8 (GraphPad Software Inc., San Diego, CA, https://www.graphpad.com). Blue and red colors in the heatmap correspond to low and high relative gene expression level, respectively.

Figure 3

Expression levels of putative DEGs associated with sex pheromone biosynthesis between the rice populations (R) and water-oat populations (W) in C. suppressalis, as determined by FPKM values. FPKM values are represented as the means ± standard error of mean (SEM) based on three biological replicates.

Figure 4

Relative expression of putative sex pheromone biosynthetic genes between the rice populations (R) and water-oat populations (W) in C. suppressalis, as determined by RT-qPCR. Relative expression values are represented as the means ± standard error of mean (SEM) based on three biological replicates. Significance analysis of the relative gene expression between the two populations was carried out by independent sample t-tests, *P <0.05, **P <0.01.